The present application relates to a light irradiation device, a fine particle analyzing apparatus, and a light irradiation method. In particular, the present application relates to a technique of irradiating a specimen in a flow channel with light.
An irradiation technique with directional light such as laser light is widely used for spectrometry, processing technology, and the like. Directional light has a single wavelength and an aligned phase. When the directional light is converged with a lens or the like, the light can be condensed at a small point. Thus, the directional light has a characteristic that an irradiation point has a high energy density.
Laser spectroscopy may be classified into linear laser spectroscopy, non-linear spectroscopy, and the like. The linear laser spectroscopy for measurement of an absorption spectrum or an excitation spectrum has high sensitivity and resolution in comparison with spectroscopy which uses an existing light source. The non-linear laser spectroscopy can provide spectrum with further high sensitivity and resolution. For example, the non-linear laser spectroscopy includes laser induced fluorescence spectroscopy, laser Raman spectroscopy, coherent anti-Strokes Raman scattering (CARS), polarization spectroscopy, resonance ionization spectroscopy, photoacoustic spectroscopy, and the like. A configuration particularly having a high time resolution provides picosecond spectroscopy or femtosecond spectroscopy.
For example, laser irradiation technology is used in flow cytometry (refer to “Cell Technology Supplementary Volume: Experiment Protocol Series, Flow Cytometry With Flexibility,” by Hiromitsu Nakauchi, Published in Aug. 31, 2006 by Shujunsha Co. Ltd., Second Edition, pp. 12 to 13). Flow cytometry is a measurement method in which living cells as a measurement subject are sorted and, for example, the function of the cells is analyzed. Cells are fed into a laminar flow, and the cells passing through the flow cells are irradiated with laser light. The irradiation causes fluorescent light or scattered light to be generated, and the light is measured. A pulse detection system detects the fluorescent light or scattered light, which is generated when the cells pass through an irradiation spot with the laser light, as an electric pulse. The pulse detection system analyzes the cells through analysis of a pulse height, a pulse width, a pulse area of the electric pulse. With the detection of fluorescent light or scattered light emitted from individual cells, the characteristics of living cells can be analyzed.